The patch-clamp technique was originally developed to study cell membrane electrophysiology by measuring very small (10−9-10−12 A) electrical currents that can flow through ion channels embedded in the lipid bilayers that form cell membranes. Such ion channels, which are typically made of proteins or assemblies of proteins, control the flow of ions (e.g. Na+, K+, Ca2+) in and out of biological cells, with the flow of ions producing weak, but measurable, electrical currents that can be sensed and recorded using the patch-clamp technique. The ion channels communicate electrical, mechanical (i.e. tactile) and chemical information into and out from biological cells and thereby participate in many different cellular processes which include the generating and timing of action potentials, the secretion of hormones, synaptic transmission, and the triggering of muscular contractions. Thus, the patch-clamp technique provides a way of determining or analyzing the effect of external electrical, mechanical or chemical stimuli on cells, and the response of the cells to such external stimuli. The patch-clamp technique, for which Neher and Sakmann were awarded the 1991 Nobel Prize in Physiology and Medicine, is useful for performing electrophysiological studies of cells to better understand cell behavior in response to external or internal stimuli, to understand exactly how the cell membrane functions, to understand certain ion-channel-related diseases and disorders, and to screen potential drug candidates for the treatment of ion-channel-related diseases and disorders or their effect on biological cells.
The patch-clamp technique is conventionally performed using a glass micropipette which must be mechanically manipulated to contact a single biological cell and to establish a “Giga-Ohm” seal with a membrane of the cell, generally by a specially-trained operator gently sucking onto the other end of the micropipette. This conventional use of the patch-clamp technique is tedious and allows the analysis of only a few cells per day.
What is needed is an apparatus that can be used to perform the patch-clamp technique under better-controlled conditions and with higher speed and precision. Additionally, it would be advantageous to have a patch-clamp apparatus that would use of smaller amounts of fluids that surround the cell and interact with it, including particular chemical species provided to stimulate the cell. Finally, what is needed is a patch-clamp apparatus that can be readily adapted to provide various types of external stimulation, including mechanical stimulation.
The present invention provides a micromachined patch-clamp apparatus that can be used for the electrophysiological study of one or more cells in a closed environment with a minimal volume (as small as a few nanoliters) of fluids surrounding and contacting the cell. The present invention is also adaptable for use with microelectromechanical actuators to provide, in certain embodiments, an instrument capable of subjecting a cell to mechanical stimulation in addition to electrical and chemical stimulation.
These and other advantages of the present invention will become evident to those skilled in the art.